Heating apparatus



Nov. 14, 950 F. o HESS HEATING APPARATUS 5 Sheets-Sheet 1 Filed June 29, 1945 MHTTORNEY Nov. 14, 1950 F. o. HESS 2,529,690

HEATING APPARATUS Filed June 29, 1945 5 Sheets-Sheet 3 iLllJl g 65* 9 957mm 76 IIIIIIIII'I'II I WITNESS Navo M, 11950 F. o. HESS HEATING APPARATUS 5 Sheets-Sheet 4 Filed June 29, 1945 m A), N

@MM 7 5r M W/ TNESS Nov. 14, 1950 F. o. HESS 2,529,690

HEATING APPARATUS Filed June 29, 1945 5 Sheets-Sheet 5 INVENTOE Fatented Nov. 1950 HEATHNG APPARATUS Frederic Selas 0. Hess, Philadelphia, Pa., Corporation of America,

assignor to Philadelphia,

Pa, a corporation of Pennsylvania Application June 29, 1945, Serial No. 602,323

24 Claims.

This invention -relates to apparatus for rapidly heating work of elongated extent, such as tubing and solid stock in the form of rods, bars, sheets and strips, for example, wherein the work moves in single line transit and in endless procession through one or more furnaces for progressively heating successive portions of the work in a controlled manner to a desired elevated temperature in one or more stages.

More particularly, the invention is concerned with an improved furnace of the type just mentioned for continuously heat treating work at such rates that considerable tonnages of stock can be handled in single line transit at a relatively high rate of speed through one or more such furnaces. By heat treating work in this manner, the actual time during which metals are under heat is relatively short and the deleterious effects of time-at-temperature, such as scaling and decarburization, for example, can be minimized.

In order. to heat treat work rapidly in single line transit, the furnace of the invention is fired by a number of direct fired burners embodied in a refractory walled chamber in which a high thermal head is produced by an immense heat release closely fitting about the traveling work piece, the heat release and thermal head developed thereby being of such magnitude that the work'may be injured in the event of work stoppage in the chamber.

Further, a fuel supply system is provided for the furnace which is extremely flexible, that is, may be operated at high turn down ratio, so that combustible fuel mixture can be supplied at the desired high pressure to the burners to accomplish rapid heating of the work and also supplied at a lower pressure when no work is passing through the furnace to fire the chamber to an elevated temperature at which the thermal head developed by the heat release will not be unduly high nor objectionable.

To produce the requisite heat release and high thermal head in the furnace, a number of direct fired burners are crowded in the refractory walled chamber. The chamber preferably is of minimum size in transverse section to accommodate the work to be heat treated and the burners are crowded at the walls of the chamber and at close range to the work, so that the gap therebetween will be relatively small.

Although not to be limited thereto, the burners may be of a type having radiators which are fully exposed to the work and at the surfaces of which burning of the combustible fuel mixture of this specification,

is accomplished, so that heating of the work will be effected both by radiant and convection components of heat transfer. Since the combustible gas mixture is supplied to the burners at a relatively high pressure the heated products of combustion are formed at an exceptionally rapid rate, whereby radiant heat will be projected from the radiators at the highest possible temperature. In addition, a high rate of convection heating is also efiected because of the high lineal velocities of the heated products of combustion passing through the relatively small gap between the work and the refractory walls in which the burners are mounted.

When a number of furnaces are closehr adjacent to one another and in end to end relation for heat treating work moving therethrough, suitable rollers may be provided adjacent the entrance and exit openings of the furnaces for guiding and feeding the work through the furnace chambers. The rollers may include single rollers between certain of the furnaces and sets of pinch rollers between other furnaces and adjacent to the entrance opening of the initial furnace through which the work passes. When the work to be heat treated is of such a character that it is distorted prior to heat treating or tends to become distorted dur ng heat treating. the sets of pinch rollers may be located and ar ranged adjacent the furnaces so that one set of pinch rollers takes a hold of a forward end of a work piece substantially at the time the rear end thereof is leaving another set of pinch rollers. With such distribution of the pinch rollers, forceable straightening of distorted work pieces is avoided since it is preferable to allow such work piecesto remain in their distorted condition rather than attempt to straighten them forceably by simultaneously gripping different parts of work pieces for an unduly long interval of time by a number of sets of pinch rollers.

The invention, together with the objects and advantages thereof, will become apparent from the following description taken in conjunction with the accompanying drawings forming a part and of which:

Fig. 1 is a side elevation of a furnace and fragmentary views of similar furnaces embodying the invention, such furnaces being arranged end to end for work or stock of elongated extent to pass therethrough to effectthe desired heating:

Fig. 2 is a vertical sectional view of the furnaces shown in Fig. l to illustrate the invention more clearly;

Fig. 3 is a transverse vertical sectional view of aeaaeec one of the furnaces and a fuel supply system for supplying to the furnaces complete and accurate mixtures of gaseous fuel and combustion supporting gas under positive pressure to obtain the desired high heat releases in the furnace;

Fig. 4 is a view more or less diagrammatically illustrating the rollers for moving and guiding the work through the furnaces and the driving mechanism therefor;

Fig. 5 is a sectional view diagrammatically illustrating one of the single rollers through which a coolant is circulated;

Fig. 6 is a horizontal plan view diagrammatically illustrating a set of pinch rollers for positively gripping and feeding the work through the furnaces;

Fig. '7 is an enlarged fragmentary sectional view of the inner lining of the furnaces to illustrate more clearly the manner in which radiant heating of the work is accomplished; and

Fig. 8 is a developed view of the peripheral surface of a section of work or stock to illustrate more effectively how successive portions of the work progressively undergo the same heat treatment in the furnaces of the invention.

Referring more particularly to Figs. 1, 2 and 3, furnaces l embodying the invention comprise refractory lined chambers i l which are relatively small in transverse section and formed with aligned openings l2 in the end walls i4 through which work l5 of elongated extent enters and leaves the chambers. Suitable rollers f6 may be positioned adjacent the openings 12 for guiding and moving the work through the chambers H.

To produce a high rate of heat liberation in as small a space as possible, a series of direct fired burners [1 extends lengthwise of each chamber 1 I and collectively takes up a major portion of the lineal distance between the end walls l4. The burners ll comprise burner blocks l8 of refractory material, and, in the illustrated embodiment, four rows of burner blocks l8 are embedded in the walls IQ of the refractory lining of each chamber II, the burner blocks in each row being in abutting relation and the burner blocks adjacent the end walls l4 being in abutting relation therewith. In this manner a maximum number of burners can be arranged compactly within each furnace ID to insure a high rate of heat liberation in a minimum amount of space.

The walls I9 of the chambers II are formed of suitable high temperature refractory material capable of withstanding the high temperatures produced in the chambers. In the illustrated embodiment the four rows of burner blocks l8 are embedded in two pairs of slanting or sloping walls I9 which diverge from the narrow top and bottom portions 20 and 2f, respectively, of each chamber II. The burner blocks 18, the inner faces of which form a part of the refractory lining for chamber I I. are formed of suitable high temperature refractory material having the requisite heat resisting and thermal conducting properties and are secured in position in the walls 19 by suitable high temperature fire brick cement.

About the walls IQ of each chamber H is provided a relatively thick wall 22 of poor thermal conductive material which is encased in an outer cylindrical-shaped metal shell 23. The wall 22 may be formed of suitable high temperature refractory material, such as fire brick, for example, which serves as an effective insulating material and possesses the requisite heat resisting properties.

Each end wall l4 comprises an annulus 24 of high temperature refractory material having the opening l2 therein and a hollow manifold 25 adjacent thereto. In the embodiment illustrated each manifold 25 is annular in form and surrounds the annulus 24. The manifolds 25 serve as the end walls for. the metal shell 23 and are secured to the latter, as by welding, for example, with the aid of angle members 26.

The manifolds 25 are formed with suitable inlet and outlet openings for circulating a coolant therethrough. This is especially desirable where a number of furnaces ID are arranged closely together in end to end relation and the rate of heat liberation by the furnaces is of such magnitude that provision must be made for preventing excessive heating of the metal parts at the ends of the furnaces.

As shown in Fig. 2, a coolant, such as water, for example, may be supplied to a number of manifolds 25 through a main conduit 21 and branch conduits 28 which in turn are secured by connections 29 to the inlets of the manifolds 25 of adjacent furnaces Ill. The coolant passes from the outlets of adjacent manifolds 25 through connections 30, branch conduits 3| and a main conduit 32. In practice, the coolant may pass from the manifolds 25 to a suitable cooling tower and pumped back to the main supply conduit 21.

The manifolds 25 are formed with integral base portions 33 which are fiat and adapted to be bolted to a suitable foundation which, as shown in Fig. 2, may comprise a number of spaced apart I-beams 34. To facilitate handling of each furnace I0 when it is positioned on and removed from the foundation, the top parts of the manifolds may be threaded to receive I-bolts 35.

A flue 36 may be provided adjacent to one of the end walls l4 of each furnace in. To regulate the flow of heated gases through the flue 36 and permit close control of the pressure of the heated gases in the chamber H, a damper 31 is provided at the top of the flue. The damper 31 may be formed of suitable refractory material in which is embedded a rod 38. To one end of rod 38 is secured a threaded member 39 passing through an opening in a vertical plate 40 secured to theshell 23. The damper 31 may be adjusted to any desired position at the top of the fine 36 by proper movement of lock nuts 4| on member 39 adapted to bear against opposite sides of the plate 40.

During operation slag may accumulate in the bottom of the chambers II. To facilitate removal of such slag the bottom of each furnace may be provided with one or more apertures which are normally closed at their lower ends by suitable plugs 42. The plugs 42 may be formed of refractory material and held in position by closure plates 43 removably secured at 44 to the bottom of each shell 23. The portion of the apertures above the plugs 42 may be filled with a loose material 45, such as sand, for example, to the level indicated at Fig. 2 which is below the bottom part 2| of the chambers II.

The burners H are of the direct fired type operable with a combustible fuel mixture having as active components thereof a gaseous fuel and combustion supporting gas which are premixed and both components of which are supplied under pressure to each burner. Although not to be limited thereto, burners which have been found especially suitable are of the type illustrated each of which, as shown most clearly in Fig. 7, comprises the burner block l8 having a central pusage which extends therethrough and terminates at acup-shaped space 48 at the face thereof formed at the rear part of the burner passage,

as indicated at 48 in Fig. 3. This accurately positions the inner ends of the sleeves 48 to each of which is secured a distributor cap or tip 50 having a number of spaced apart grooves or slots 5| atthe periphery thereof for subdividing the gaseous fuel mixture and causing a plurality of gas streams to be discharged from the underside of the tip at the inner ends of the grooves 5| and at which region the burner flames are produced and maintained.

The sleeves 48 are urged against theseats at 48 by springs 52 disposed about hollow flexible connections 53 which are secured at one end to the sleeves and at the opposite end to conduits 54 secured to plates 55 at openings therein, each plate 55 being mounted on the casing 23 by a pair of brackets 55. The springs 52 are held between the plates 55 and flanges 51 at the outer ends of the sleeves and urge the latter toward the seats at 49. e 1

As shown most clearly in Figs. 1 and 3, each row of burners I! is connected by the conduits 54 to amanifold 58 which extends lengthwise of the furnace I8, and the two manifolds 58 at each side of the furnace are connected at regions intermediate the ends thereof by conduits 58 to a conduit 50. As shown in Fig. 1, a manually operable control valve 54a is provided in each conduit 54 for individually regulating the supply of combustible gas mixture to the burners l1. The conduit 58 at opposite sides of the furnace in are connected to a conduit 5| through which a combustible fuel mixture is supplied under pressure from the fuel supply system.

In order to produce the desired high rate of heat liberation-in the furnaces 10, it is desirable to supply complete and accurate mixturesof gaseous fuel and combustion supporting gas under positive pressure to the burners II. In the embodiment illustrated this is accomplished by a fuel supply system including a mixer 52 to which are introduced a gaseous fuel from a conduit 68 and a combustion supporting gas, such as air or mixture of air and oxygen, for example.

The conduit 53 is connected to the mixer 52 by a conduit 54 in which are provided a manually operable valve 55, an electromagnetically operable valve 56 and 'a gas pressure regulator 61. The gas pressure regulator 61 includes a partition 58 between the inlet and outlet there of having an aperture forming a valve seat which cooperates with a valve 68 secured to a stem 78. The stem 18 passes through and is secured to a main diaphragm H and an auxiliary diaphragm 72 arranged to form top and bottom chambers 13 and 14. A spring 15 is disposed about the upper part of stem 18 and tends to urge the valve 58 upwardly.

In order, to supply gaseous. fuel to the mixer 52 at asubstantially constant pressure, such as atmospheric pressure, for example, the spring '18 maybe adjusted by, a nut 15 so that the weight of the stem and parts carried thereby is balanced by the spring. A short tube 11 at the discharge side of valve 58 communicates with the bottom chamber 14.- The valve 58 moves toward and from its seat responsive: to changes in pressure at the discharge-side of the valve 88, such movement of the valve being effective to maintain the gas discharged from the regulator 51 at substantially a constant pressure.

Combustion supporting gas, such as air from the atmosphere, for example, is drawn'through a filter 18 and conduit I8 to the mixer 52. The air in conduit 18 isapproximately at atmospheric pressure or at a slightly negative pressure due to the pressure drop effected through the filter 18. In order that the gaseous fuel will enter the mixer 52 at approximately the same pressure as the air, the air conduit 18 is connected by a tube to the top chamber 13 of the gas pressure regulator 51. Any variations in air pressure in conduit 18 are reflected back to the top chamber 13. Thus, valve 58 not only responds to changes in pressure at the discharge side of the valve, as just described, but also to changes in pressure of the combustion supporting gas entering mixer 52. Hence, thegaseous fuel and combustion supporting gas can be introduced into the mixer at substantially the same pressure.

In order to increase the temperature at which the burners I! can be operated, oxygen maybe mixed with the air to provide oxygen enriched air as the combustion supporting gas component of the combustible fuel mixture. As shown, oxygen from a suitable source of supply may be delivered through a conduit 8| in which are promixture in conduit 18, so that the gaseous fuel the same pressure as will enter the mixture at that of the air and oxygen mixture.

The mixture 52 is connected by a conduit 88 to the inlet of a compressor 81, the outlet of which is connected to the conduit 5|. Due to thesuction effect produced by the compressor 81, gaseous fuel and combustion supporting gas are drawn into the chamber 88 of the mixer 82 through diametrically opposite ports formed by square orifices in the wall of the chamber and square orifices in a hollow piston 88, as indicated at 88 and 8l, respectively, in Fig. 3.

The piston 88 is rotatably mounted on a spindle 82 which is connected at its lower end to a diaphragm 83 forming a chamber 84 at the lower part of the mixer 62. This chamber is connected by a tube as to the conduit 19 through which combustion supporting gas flows to the mixer. The piston 88 can be turned or rotated on the spindle 82 by a crank. 85, thereby adjusting the position of the orifices in the piston 88 in a horizontal direction with respect to the orifices in the wall of chamber'88 and hence accurately de- The vertical position that piston 88 assumes 7 in chamber .8 determines the extent of overlap of the orifices in the chamber wall and piston in a vertical direction, and hence the sizes of the ports formed by these orifices through which gaseous fuel and combustion supporting gas can pass. The vertical position that piston I! assumes is dependent upon the pressure of the incoming combustion supporting gas in chamber N, the downward force exerted by the weight of the piston II, and the suction effect of the compressor in chamber 88. The greater the de-.

mand upon the compressor 81, that is, the greater the rate at which combustible fuel mixture can' flow to the furnace III, the greater will be the suction effect in chamber 88 and hence the higher will be the position that the piston 89 assumes therein to increase the sizes of the ports formed by the orifices through which the gaseous fuel and combustion supporting gas enters the mixer 82.

As shown, the compressor 81 may be of a positive displacement type driven by an electric.

of the compressor which is normally open and closes when the back pressure of the compressor builds up sufficiently which occurs, for example,

when the compressor is shutdown. The closing of check valve IOI cuts off the suction effect of the compressor 81 from the mixer 62 whereby the piston 29 will fall and close the inlet ports for the gaseous fuel and combustion supporting gas.

In order to regulate the heating effected by thefurnaoes III, a suitable control system may be provided including a thermo-couple I02 arranged at the inner refractory lining of each chamber II. As shown in Fig. 3, the thermocouple III2 is embedded in the wall of the furnace in adjacent the narrow top part 20 of the inner lining, so that it will be subjected to the high temperatures produced in chamber I I. The thermo-couple I02 is connected by conductors I 03 and I to a suitable potentiometer control I08 of any well known and conventional type which is connected by conductors I06 and III! to a source of electrical energy.

The electromagnetically operable valves 68 and II are connected in series to the potentiometer control "I by conductors I08, III! and H0. The control system just described is so adjusted that when the chamber II reaches a predetermined abnormally high temperature, the electromagnetically operable valves 86 and 83 close and shut off the supply-of gaseous fuel and oxygen to the mixer 62 and hence cut off the supply of combustible fuel mixture to the burners II of the furnaceJIi. I

If desired. the electric motor I! may be connected to the potentiometer control I05 so that it will also be disconnected from its source of electrical energy and shut down compresser 81 responsive to a predetermined abnormally high temperature in the chamber II to which the thermo-couple I02 is subjected. However, in cerasaasao 8 tain instances it may be desirable to allow compressor 81 to continue to operate after the supply of gaseous fuel and oxygen are cut off by the closing of electromagnetically operable valves II and It, so that air from the atmosphere will continue to be supplied to the burners I! to eflect cooling of the chamber I I and hasten the lowering of the furnace temperature.

It has already been pointed out that the work I 5, which is of elongated extent, may be progressively moved through a number of furnaces It in end to end relation by the rollers It. The driving means for the work It may include the single rollers I6 and sets of pinch rollers H2 and III arranged at spaced intervals between the single rollers It, as shown in Fig. 4. The rollers I8 and pinch rollers H2 and II adjacent the openings I2 prevent sagging of work during heating and keep work centered in the chambers II.

When the work I5, such as solid stock or tubing, for example, is relatively heavy and substantially straight and no distortion problem is encountered, single rollers Il may be employed satisfactorily for frictionally driving the work through the furnaces III. However, when it is desired to effect heating of work relatively light in weight and which initially may be in a distorted condition or tends to become distorted during heat treatment, the pinch rollers H2 and I I4 are necessary because of slippage taking place when single rollers I6 are employed alone. This is especially true when the work is distorted, and, due to the longitudinally bowing of the work, the latter does not engage or snugly rest on one or more of the rollers I6. I

The pinch rollers I I2 and 4 may be arranged at such intervals between the single rollers I8 that one pair or set of such pinch rollers or a number of such sets may simultaneously grip a single length of work, such as solid stock or tubing, for example. However, when the work is of relatively light weight and is initially distorted or tends to become distorted due to heating, it is usually preferable to allow such work to remain in its distorted condition rather than straighten it forceably by simultaneously gripping different parts thereof for an unduly long period by a number of sets of pinch rollers H2 and H4. Hence, when the work piece I5 is of such length that it extends through three furnaces I0, as shown in Fig. 4, for example, the set of pinch rollers H2 and II disposed between adjacent furnaces I0 is just beginning to take a hold of the forward end of the work piece at the time the rear end thereof is leaving the set of pinch rollers II 2 and I ahead of the first furnace I0 in which initial heating of the work is effected. In heating work which is relatively heavy in weight and no severe distortion problem is encountered, the pinch rollers I I2 and Ill may be arranged in any desired spaced apart relation.

As shown in Fig. 5, each roller I6 is hollow and mounted on a hollow shaft II5 which is fournaled in bearings II6 supported in any suitable manner adjacent an end of the furnace I0. Rotary union connections I" may be provided at the ends of the shaft II5 to which flexible conduits II8 are connected for circulating a coolant, such as water, for example, through the shaft IIS and hollow roller I6.

The bottom rollers II2 of each pair of pinch rollers may be identical to the rollers I5, as shown in Fig. 6, and parts similar to those illustrated in Fig. 5 are referred to by the same reference numbers. Each top roller I II is also hollow and mounted on a hollow shaft 8 which is journaled at Ilsa at the upper ends of heavy metal arms I20, the lower ends of which are lournaled at I2Ila on the shaft H5. End connections similar to those on each shaft H5 are also provided at the ends of the shafts I I9 for circulating a coolant therethrough. The top rollers II4 bear against the top surfaces of the work pieces, and, since these rollers are weighted down by the heavy supporting arms I20, the work is snugly pressed downwardly against the bottom rollers H2.

The rollers I6 and H2 may be driven in any suitable manner. As diagrammatically shown in Fig. 4, this may be accomplished by endless chains I2l connected to gears H2 and I23 mounted on the shafts H5 and I24, respectively. The top rollers Ill may be driven by endless chains 44; connected to gearing fixed to shafts IIS and H9, respectively. The shafts I24 in turn are driven by endless chains I25 connected to gears mounted on the shafts I24, and one of the shafts I24 may be fixed to the shaft of an electric driving motor I26 connected by conductors I21 and I28 to a suitable source of electrical energy. The motor I26 may be provided with an adjustable'rheostat I29 in series with a field winding I30 connected across the conductors I21 and I28 for varying the motor speed and hence adjusting the speed at which the rollers I6, H2 and Ill are. driven for moving the work through the furnaces II).

The fuel supply system described above is capable of delivering to the burners II accurate and complete mixtures of gaseous fuel and combustion supporting gas at the requisite high pressures necessary in order to obtain the desired high heat releases in the furnaces III. By turning the piston 89 within the mixer 62 by the crank 96, therelative sizes of the ports 90 and 9| can be accurately adjusted to deteremployed in mine the desired ratio of combustion supporting 1 gas to gaseous fuel entering the mixer 62.

Maximum efficiency and maximum heat input is obtained in the furnaces II] when the ratio of combustion supporting gas to gaseous fuel is such that a completely combustible fuel mixture is formed with no excess of either component of the mixture, and in such case a neutral atmosphere is produced in the chambers II of the furnaces I0. When a, reducing atmosphere is desired in the furnaces I0, the ratio of combustion supporting gas to gaseous fuel is adjusted so that there will be a slight excess of the gaseous fuel componentin the combustible fuel mixture.

While mixing of the combustion supporting gas and gaseous fuel component is effected substantially at atmospheric pressure in the mixer 62, as described above, the compressor 81 is capable of delivering the combustible fuel mix-- ture to the burners II at pressures as high as 3 pounds per square inch which is equivalent to about 83 inches of water column. However,

' the combustible fuel mixture may be delivered to the burners I1 at pressures of 5 pounds per square inch and higher. The maximum delivery pressure may be controlled, of course, by proper adjustment of the gas pressure governor 98 at the outlet of the compressor 81.

The combustible fuel mixture is delivered from the compressor 81 through the conduits GI, 60 and 59 to the manifolds 58 associated with each row of burners I1, and from the manifolds 58 the fuel mixture flows through the branch conduits 54 to each of the burners ii. The distributor caps or tips III in the burners II subdivide the combustible fuel mixture supplied thereto, whereby a number of small gas streams are discharged from the under sides of the tips 50 at which regions the burner flames are produced and maintained, as explained above. Hence, a number of flames are maintained about the peripheral surface of each tip 50 which project outwardly therefrom into the cup-shaped spaces 46 in which burning and combustion of the fuel mixture takes place. The flames are closely adjacent to and follow the cup-shaped refractory walls to heat the latter to high incandescent temperatures.

The combustion spaces 46 serve as radiators and are heated to incandescent temperatures of 2700 to 3000 F. when a combustible mixture is which the combustion supporting gas consists entirely of air and the gaseous fuel is ordinary city gas having a rating of about 530 B. t. u. per cubic foot. Since the inner faces of the burner blocks I8 form a, part of the inner refractory lining of entire surfaces thereof are fully exposed to the work pieces I5 which pass through the chamber, all surface regions of successive portions of the work pieces are subjected to intense radiant heat projected from the four rows of burners II.

In order to effect high speed heating of work pieces, it is desirable to crowd as many burners II as possible in the chambers II which are relatively small in transverse section and of such length that the desired heating effect is accomplished therein. In this manner an immense heat release closely fitting about the traveling work piece is attained; and the thermal head, that is, the temperature differential between the radiators 46 and the surfaces of the work, is at a maximum. Hence, in practicing the invention it is preferable to provide chambers II which are of minimum size in transverse section to accommodate the work pieces to be heat treated and to crowd the burners I! about the walls of the chambers II at close range to the work pieces, so that the gap or space between the inner walls and the work is relatively small in contradistinction to usual furnace practice and in a range varying from about 1 and /2 to 3 inches.

By constructing the furnaces II! in the manner I described above exceedingly rapid heating rates are efiected. This may be attributed to the high thermal head referred to above and to the high rate of radiant heat transfer associated therewith which is proportional to the difference between the fourth powers of the absolute temperatures of the radiators 46 and the surfaces of the work pieces. Since each chamber II in transverse section is preferably of minimum size to accommodate the work pieces to be heat treated and the burners I 'I are at close range to the work, the products of combustion whip through the cells or chambers II and are discharged therefrom at extremely high lineal velocities.

Inasmuch as the rate of heat transfer to the work by convection is proportional to the speed at which the heated products of combustion flow past the heat receiving surfaces of the work, it will be evident that the high lineal velocities at which the hot convection medium whips through the cells or chambers II contributes significantly to the rapid heating of stock or work passing in single line transit and in an endless procession the chamber II and the,

through one or more chambers ll. Hence, by providing furnaces l having chambers H which are relatively small in transverse section and crowding as many burners H as possible therein at close range to the work, both the radiant and convected components of heat transfer are accelerated to a substantial degree.

The heated products of combustion are formed at the burners at an exceptionally rapid rate so that radiant heat will be projected from the radiators 41 at the highest possible temperature. To produce the high incandescent temperatures at the radiators 41, therefore, the combustible fuel mixture is supplied to the burners I! at a relatively high pressure by the fuel supply system, as explained above. The high lineal velocities of the heated products of combustion results because of the relatively narrow path of flow provided for these heated gases between the inner walls of the chamber H and the heat receiving surfaces of the work.

In view of the exceedingly high rate at which the heated products of combustion are formed at all of the burners H which are crowded in a relatively small chamber II, it may be necessary in many instances to provide the furnaces ID with the dues 36 through which the heated gases may escape. While heated products of combustion are discharged from the furnaces in through the end openings I! about the work pieces IS, the rate at which combustible fuel mixture is supplied to all of the burners H in a single furnace l0, especially when the latter is being operated at full capacity, is such that the flues 36 may be necessary in order to permit the heated products of combustion to escape from the chambers H at an adequate rate to insure a high rate of heat liberation in the furnace chambers.

The dampers 31 are preferably adiusted at the tops of the flues 36 so that the pressure of the heated products of combustion in the chambers H is above atmospheric pressure by an amount which may be equivalent to several inches of water column. By maintaining the pressure of the heated products of combustion in the chambers H above that of atmospheric, a back pressure is built up in the cup-shaped spaces or radiators 46 which permits the combustible fuel mixture to be supplied at a higher delivery pressure than would otherwise be possible and hence increase the high incandescent temperatures produced at the radiators l6.

In order that the improvements embodied in furnaces III of the invention may be better understood, reference to a furnace for heating solid stock and tubing up to 1 in diameter and generally like that illustrated in the drawings may be helpful. In such a furnace the diameter of the casing 23 is about 2'7" and the length of the chamber II is about 33". Ten burner blocks l8 are arranged in abutting relation in each of two bottom rows and eight burner blocks are arranged in each of two top rows, the flue 36 taking up the space of two burner blocks in the top rows, in a manner like that shown in Fig. 2.

The burner blocks l8, which are formed of high temperature refractory material, are approximatelv 3 /4" square in section and embedded in the walls It, as shown in Figs. 2 and 3. The chamber H in transverse section is like that shown in Pig. 3, the maximum vertical and horizontal dimensions being about 6%". The openings II in the end walls l4 at their narrowest region are about 2%" in diameter to accommodate s'olid stock or tubing up to 1%" in diameter.

In order to permit slag to collect in the bottom of the chamber II. the latter is formed with pairs of walls is diverging from the narrow top and bottom portions 20 and 2 I, respectively. The two bottom rows of burner blocks i 8 are angularly spaced apart 120 while the two top rows of burner blocks are angularly spaced apart about as indicated in Fig. 7. This permits all four rows of burners H to be spaced at close range to the work and project radiant heat more or less uniformly on all surface regions thereof. Further, this arrangement of the burners l1 provides the widest possible trough at the bottom 2| in which slag may collect without injuring the bottom rows of burners from which radiant heat is directed to the bottom of the work pieces.

When solid stock or tubing 1 in diameter passes through the chamber i l, the distance from t e inner faces of the top burners H to the surface of the work, which is indicated at a in Fig. 7, is about 2 and the distance from the inner faces of the bottom burners H to the surface of the work, which is indicated at b in Fig. '7, is about 2%". Since the burners II are of a type in which substantially complete combustion of the fuel mixture may be accomplished within the confines of the radiators 41, the inner faces of the burners I! can be positioned at such close range to the work without flame impingement on the work surfaces.

The minimum size of each end opening 12 is indicated by a circle in Fig. 7. The radial distances from the inner faces of the top and bottom burners to this circle are indicated at c and 11, respectively. Any point on the circle i2 nearest to the inner face of a burner I! may be considered as being on a line extending lengthwise of chamber II and connecting corresponding points at the peripheries of the entrance and exit openin'zs. It will be seen that the radial distances 0 and d from such points to the inner faces of the top and bottom burners I1, respectively, are less than and do not exceed the maximum dimension at the inner faces of the burner blocks l8. With the burners I! being positioned such distances from the peripheral edges of the entrance and exit openings l2, the maximum number of burners l1 practicab e is crowded into the chamber II, as will be evident from Fig. v3, whereby the maximum heat liberation will be effected for a chamber of a given size without the likelihood of the bottom burners being injured from slag colecting collecting in the bottom part of the chamber.

A furnace of the character inst referred to may be operated with a combustible fuel mixture of air and propane having a rating of 2550 B. t. u. per cubic foot. When such a fuel mixture, having a slight excess of propane to produce a reducing atmosphere, is supplied to the burners i! at a delivery pressure equivalent to about 19 inches of water column, the thirty-eight burners are capable of liberating about 918,000 B. t. u. per hour. With such heat liberation the single furnace being described is operative to heat copper alloy and brass stock and tubing to a temperature of about 1600 F. at a rate of about 1000 pounds per hour. In heating solid bars of brass or copper alloy /2" in diameter, the speed of travel of the work through the furnace is about 23 feet per minute: and for bars 1 /2" in diameter, the speed of travel of the work is about 2 feet per minute. For tubing the speed of travel will be dependent upon the weight of the tubing per unit length.

When the furnace is being operated as just described for heating brass and copper alloys. the radiators I! are maintained at a temperature of about 2800 to 2900" Rand well above the melting point of any of the'alloys involved. The high temperatures maintained within the-chamber II is indicated by the fact that the temperature of the fluegases escaping from the chamber of such a furnace is about 2500 F. Further, the heated products of combustion will flow past'the heat receiving surfaces of the work at lineal velocities of about 75 to 100 feet per second.

. When the furnace described above and ike that illustrated is supplied with a combustible fuel mixture of 'air and ordinary city gas having a rating of about 530 B. t. u. per cubic foot, and the ratio of air to gas is 4 to 1' to produce a neutral atmosphere, for example, the thirty-eight burnew are capable of liberating. 1,900,000 B. t. u. per hour when the fuel mixture is supplied to the burners at a pressure equivalent to about 60 inches of water column. Such fuel mixture delivery pressures have been used for many heat treating applications in furnaces of the character described, and in particular cases fuel mixture delivery pressures as high as 80 inches of water column may be necessary and desirable.

-When the furnace is being operated at such fuelmixture delivery pressures it is necessary for work to be traveling through the furnace chamber to absorb the liberated heat. If work pieces were not passing through the chamber of the furnace and the burners were being operated at the high fuel mixture delivery press res just mentioned, the temperatures produced in chamber II would reach an abnormally h gh value. Hence, when no work is traveling through the furnace chambers, the fuel mixture delivery pressure should be reduced to a low value in a range equivalent to about 6" of water column, for example, by proper adjustment of the valves 54a.

The fuel supply system described is extremely flexible and "possesses a high turn down ratio, whereby mixture delivery pressures as high as 80 inches of water column may be produced for high heat liberation when the burners I! are operated at full capacity; and pressures as low as 6 inchesof water column may beproduced, for example, so that the thermal head developed by the heat release will prevent the chamber I I'from reaching abnormally high temperatures when no work is passing therethrough. At such low mixturedelivery pressures the chamber II can be maintained at an elevated'temperature approaching that maintained when rapid heat treating of work is being effected at higher mixture delivery pressures. .In'other words, the chamber II can lie-maintained at temperature at low gas mixture delivery pressures so that the pressure can be immediately increased when desired to commence heattreating of work. This is possible because of the ihigh turn down ratio of the fuelsupply system'whereby an accurate mixture of gaseous fuel and combustion supporting gas can be supplied to theburners I'l throughout the entire operating range of gas mixture delivery pressures required and varying, for example, from 80 to 6 inches of water column. 1 Y

The foregoing illustrates the fundamental concept 10f theprinciples of the invention to provide high speedheating unitswhich require accurate coordination between precision work feeding rates and firing byburners operated at unusually high fuel mixture delivery pressures. It is for this reason that-a suitable control system, as described above, for example, is provided to shut oil! the supply of combustible fuel mixture to the burners I 'I in the event of work stoppage. When work Jams or stops in a furnace and the temperature in chamber II rises to an abnormally high value, the potentiometer control I05 responds to the thermo-couple I82 and closes the electromagnetically operable valves 66 and 83 to shut off the supply of combustible fuel mixture to the burners I1, as previously described. The compressor 81 may continue to operate in such case to supply air alone to the burners I1 to hasten the lowering of temperature in the chamber I I from the abnormally high value, as pointed out above.

In addition, the electromagnetically operable valves I56 and 83 may be arranged to close and shut oil! the supply of combustible fuel mixture to the burners I1 of each furnace IIl when work is not being fed thereto. This may be accomplished by providing for each furnace ill a photoelectric cell associated with a suitable amplifying unit which is connected in conductors I08 and I Ill. The photoelectric cell and a light source are positioned at the inlet end of each furnace at o posite sides of the work which prevents the photoelectric ce'l from receiving a beam of light from the light source as long as work is being fed to the furnace. Under such conditions the circuits for the electromagneticallv operable valves 66 and 83 remain completed and combustible fuel mixture is supplied to the burners I'I. However, when work is not being fed to the f rnace I0 and the photoe ectric cell does receive a beam of light from the light source, the amplifying unit responds to open the circuits for the electromagnetically operable valves 66 and 83 which close and shut off the supply of combustible fuel mixture to the burners IT. The photoelectric cell and light source may be protected in any suitable manner, as by water cooling, for example, to prevent overheating of these parts.

The radiant component of heat transfer is effected by each burner III in the manner diagrammatically illustrated in Fig. 7. The burners H are desirably distributed about the chamber II so that there will be overlapping of radiant heat components from the individual burners, whereby uniformity of heating may be effected about the entire peripheral surface of the work.

In Fig. 8 is shown a developed view of a section of a work piece diagrammatically illustrating the manner in which transfer of radiant heat takes place. At each instant of travel through the chamber II small localized areas of the work piece, which are momentarily directly opposite the radiators 41, are heated more intensely at I32 at the centers of such areas. However, such heating effects of greater intensity immediately spread outwardly from the centers in a manner that may be likened to the ripples spreading radially outward at the surface of a body of water from the region at which an object falls into the water. The spreading of the intense heating effects received at a particular instant during the travel of the work through the chamber II is diagrammatically indicated in Fig. 8 by the circles I33 of increasingly larger size. As each successive por tion of a work piece travels through chamber II of a furnace, all regions of each portion are heated uniformly by both the radiant and convected components of heat transfer, so that each work piece undergoes the same heat treatment inch by inch along its length.

A further advantage accruing is that the actual time during which metals are under heat is relatively short and the deleterious effects of time-attemperature, such as scaling and decarburizatlon, for example, can be minimized. Thus, in the application referred to above for heat treating copper alloys and brass work pieces in a furnace having a capacity of about 1000 pounds per hour, the time under heat for rods of /2" diameter is about 8 seconds and for rods 1 /2" in diameter is about 93 seconds.

It will now be understood that an improvement has been provided for continuously heat treating work at such rates that considerable tonnages of stock can be handled in single line transit at a relatively high rate of speed through one or more furnace units. In certain applications a single furnace l may be employed to accomplish the desired heat treatment of work which, for example, may involve heating of non-ferrous metals for annealing operations or heating of ferrous metals to effect hardening thereof. In each instance the size of the furnace chamber in transverse section will depend upon the size of the work or stock to be heat treated, and the chamber in each case must necessarily be of sufllcient length to accomplish the desired heating therein and which may vary, for example, from 13" to 8 or more feet in length.

In other applications it may be desirable to employ a number of furnaces In which are close together and in end to end relation, as shown in Fig. 4. In such cases the initial furnace may effect heating of work to a predetermined elevated temperature and one or more additional furnaces may effect heating of work to successively higher predetermined temperature levels. By employing a number of furnaces I0 greater flexibility of operation is afforded in that heating of work to successively higher temperatures may be accomplished at temperature levels of stages which can be changed at will depending upon the kind of work being handled and metallurgical characteristics desired.

The furnace chambers II in transverse section may be of different shape from that illustrated to accommodate rods, strips, bars and other work pieces of various shapes. Rollers may be provided in the interior of chamber II when such an arrangement is deemed advisable for a particular heat treating application. In such case one or more burner blocks in the two bottom rows may be omitted to accommodate the roller and shaft associated therewith, which may be of a type like that shown in Fig. through which a coolant, such as water, for example, may be circulated.

Although a single embodiment of the invention has been shown and described, it will be apparent that various modifications and changes may be made without departing from the spirit and scope of the invention, as pointed out in the following claims.

What is claimed is:

1. Apparatus for heating work of elongated extent including a furnace comprising structure forming a refractory walled chamber having end walls each provided with an aperture therein, the apertures serving as entrance and exit openings at opposite ends of the furnace for work adapted to pass through the chamber, means for firing the chamber to an elevated temperature including a number of burners comprising blocks of refractory material embodied in the refractory walled chamber, fuel supply means for delivering to the burners a combustible fuel mixture having as active components thereof a gaseous fuel and combustion supporting gas, said fuel supply means including a compressor for delivering both of said components under positive pressure to the burners, means connected to the compressor for supplying thereto the gaseous fuel and combustion supporting gas components, and means responsive to a condition affected by an abnormally high temperature in the chamber for shutting off the supply of gaseous fuel to said compressor and causing the latter to deliver only combustion supporting gas under pressure to the burners.

2. Apparatus for heating work of elongated extent including a horizontal furnace comprising structure forming a refractory walled chamber having end walls each provided with an aperture therein, the apertures serving as entrance and exit openings at opposite ends of the furnace for work adapted to pass through the chamber, means including burners for firing the chamber to an elevated temperature, fuel supply means for delivering to the burners a combustible fuel mixture having as active components thereof a gaseous fuel and combustion supporting gas, said fuel supply means including a compressor for delivering both of said components under positive pressure to the burners, means connected to the compressor for supplying thereto said active components including conduit means for the gaseous fuel which is adapted to be connected to a source of supply, normally-open valve means connected in said conduit means, and thermal means responsive to an abnormally high temperature in the chamber for closing said valve means and causing said compressor to supply only combustion supporting gas under pressure to the burners.

3. Apparatus for heating work of elongated extent including a horizontal furnace comprising structure forming a refractory walled chamber having end walls each provided with an aperture therein, the apertures serving as entrance and exit openings at opposite ends of the furnace for the work and through which heated gases pass from the chamber about the work when the latter passes through the chamber, means including burners for firing the chamber to an elevated temperature, fuel supply means for delivering to the burners a combustible fuel mixture having as active components thereof a gaseous fuel and combustion supporting gas, said fuel supply means including mechanism for delivering both of said components under positive pressure to the burners, and means connected in said fuel supply means operable responsive to an abnormally high temperature in said chamber for shutting off the supply of the gaseous fuel and causing said mechanism to deliver only combustion supporting gas under pressure to the burners.

4. Apparatus for rapidly heating work of elongated extent including a horizontal furnace comprising structure forming a refracto:y walled chamber having end walls each provided with an aperture therein, the apertures serving as entrance and exit openings at opposite ends of the furnace for the work and through which heated gases pass from the chamber about the work when the latter passes in a single line transit and in endless procession through the chamber; means for firing said chamber to an elevated temperature including a number of burners in the refractory walled chamber between the end walls thereof, the inner face of each burner forming a part of the inner refractory lining for the chamber and serving as an independent source of heat; fuel supply means for delivering to the burners a combustible gas mixture having a combustible gas and combustion sup- .sure at which the mixture may be supplied to the burners by the fuel supply means being correlated-to effect rapid heating of successive portions of the work adapted to pass through the chamber by an intense heat release at a high thermal head; such heat release and thermal head developed thereby being of such magnitude that the temperature in the refractory walled chamber will rise to an abnormally high value and cause the work to be injured in the event of work stoppage in the chamber; and means associated with said fuel supply means operable responsive to rise in temperature in the chamer to the abnormally high value for shutting off the delivery of gaseous fuel and causing said device to supply only combustion supporting gas under pressure to the burners to promote cooling in the chamber.

5. Apparatus for heating work of elongated extent including a furnace comprising structure forming a refractory walled chamber, a wall at each end of said furnace including a centrally disposed annulus of refractory material and a hollow manifold about the annulus, said annuli forming entrance and exit openings for the work at opposite ends of said chamber, each of said manifolds having inlet and outlet openings for circulating a coolant therethrough, said structure including a number of rows of burners comprising blocks of refractory material extending lengthwise of said chamber between the entrance and exit openings, the blocks in said rows being in abutting relation and the end blocks in each of said rows being in abutting relation with the annulus adjacent thereto, the inner face of each burner forming a part of the refractory lining for said chamber and serving as an independent source of radiant heat, and means to supply gaseous fuel individually to each burner for combustion at the inner face thereof to heat the latter to incandescence.

6. Apparatus for heating work of elongated extent including a furnace comprising structure forming a refractory walled chamber, a wall of refractory material at each end of said chamber having an aperture therein, said apertures serving as entrance and exit openings at opposite ends of the furnace for the work and through which heated gases are discharged from the chamber about the work when the latter passes through the chamber, a hollow manifold at each end of the furnace adjacent to said end walls, each of said manifolds having inlet and outlet openings for circulating a coolant therethrough, said structure including a number of rows of burners comprising blocks of refractory material extending lengthwise of said chamber between the entrance and exit openings, the blocks in said rows being in abutting relation and the end blocks in each of said rows being I forming a refractory walled chamber, a wall in abutting relation with the end walls, the inher face of each burner forming a part of the refractory lining for said chamber and serving as an independent source of radiant heat, and means to supply gaseous fuel individually to each burner for combustion at the inner face thereof to heat the latter to incandescence.

7. Apparatus for heating work of elongated extent including a furnace comprising structure of refractory material at each end of said chamber having an aperture therein, said apertures serving as entrance and exit openings at opposite ends of the furnace for the work and through which heated gases are discharged from the chamber about the work when the latter passes through the chamber, a hollow manifold at each end of the furnace adjacent to said end walls, each of said manifolds having inlet and outlet openings for circulating a coolant therethrough,

said structure including a number of rows of burners comprising blocks of refractory material extending lengthwise of said chamber between the entrance and exit openings, the blocks in said rows collectively taking'up a major portion of the lineal distance between said end walls, the inner face of each burner forming a part of the refractory lining for said chamber and serving as an independent source of radiant heat, and means to supply gaseous fuel individually to each burner for combustion at the inner face thereof to heat the latter to incandescence.

8. Apparatus for heating work of elongated extent including a furnace comprising structure forming a refractory walled chamber, a wall of refractory material at each end of said chamber having an aperture therein, said apertures serving as entrance and exit openings at opposite ends of the furnace for the work and through which heated gases are discharged from the chamber about the work when the latter passes through the chamber, a hollow manifold at each end of the furnace adjacent to each of said end walls, said manifolds having iniet and outlet openings for circulating a coolant therethrough, a number of direct fired burners for the furnace comprising a row of burner blocks of refractory material embodied in the refractory walled chamber and extending lengthwise thereof between the end walls, the burner blocks in said row collectively taking up a major portion of the lineal distance between said end walls, the inner face of each burner block forming a part of the refractory lining for said chamber and serving as an independent source of heat, and means to supply combustible fuel individually to each burner.

9. Apparatus for heating work of elongated extent including a horizontal type furnace comprising structure forming a refractory walled chamber including a floor and roof and opposing side walls, the maximum vertical height and maximum width of said chamber being approximately the same in extent, a wall of refractory material at each end of said chamber having an aperture therein, said apertures serving as entrance and exit openings at opposite ends of the furnace for the work and through which heated gases are discharged from the chamber about the work when the latter passes through the chamber, said structure including rows of burners at the opposing side walls extending lengthwise of said chamber between the entrance and exit openings, the burners in each of said rows collectively taking up a major portion of the lineal distance between said end Walls, the inner face of each burner forming a part of the refractory lining for said chamber and serving as an independent source of heat, and means to supply gaseous fuel individually to each burner.

10. Apparatus for heating work of elongated extent including a furnace comprising structure forming a refractory walled chamber, a wall of refractory material at each end of said chamber assaeao having an aperture therein. said apertures serving as entrance and exit openings at opposite ends of the furnace for the work and through which heated gases are discharged from the chamber about the work when the latter passes through the chamber. a hollow manifold at each end of the furnace adjacent to each of said end walls, each of said manifolds having inlet and outlet openings for circulating a coolant therethrough, a number of direct fired burners for the furnace comprising a series of burner blocks of refractory material embodied in the refractory walled chamber and extending lengthwise thereof between the end walls, the burner blocks in said series collectively taking up a major portion of the lineal distance between saidend walls, the inner face of each burner block forming a part of the refractory lining for said chamber and serving as an independent source of heat, and means to supply combustible fuel individually to each burner.

11. Apparatus for heating work of elongated extent including a compact furnace comprising structure forming a refractory walled chamber, a wall of refractory material at each end of said chamber having an aperture therein, said apertures serving as entrance and exit openings at opposite ends of the furnace for the work and through which heated gases are discharged from the chamber about the work when the latter passes through the chamber, said structure including a number of rows of burners comprising blocks of refractory material extending lengthwise of said chamber between the entrance and exit openings, the blocks in each of said rows collectively taking up a major portion of the lineal distance between said end walls, the radial distance from the inner faces of said blocks to the nearest line connecting corresponding points at the peripheries of the entrance and exit openings not exceeding the maximum dimension at the inner face of a block, the inner face of each block forming a part of the refractory lining for said chamber and serving as an independent source of heat, and means to supply gaseous fuel individually to each burner.

12. Apparatus for heating work of elongated extent including a compact furnace comprising structure forming a refractory walled chamber,

a wall of refractory material at each end of said chamber having an aperture therein, said apertures serving as entrance and exit openings at opposite ends of the furnace for work of elongated extent and through which heated gases are discharged from the chamber about the work when the latter passes through the chamber, a number of .direct fired burners for the furnace comprising a row of blocks of refractory material embodied in the refractory walled chamber and extending lengthwise thereof between the end walls, the blocks in said row collectively taking up a major portion of the lineal distance between said end walls, the radial distance from the inner faces of said blocks to the nearest line connecting corresponding points at the peripheries of the entrance and exit openings not exceeding the maximum dimension at the inner face of a block, the inner face of each block forming a part of the refractory lining for said chamber and serving as an independent soulce of heat, and means to supply combustible fuel individually to each burner.

13. Apparatus for heating work of elongated extent including a compact furnace comprising structure forming a refractory walled chamber, a wall of refractory material at each end of said chamber having an aperture therein, said aperturu serving as entrance and exit openings at opposite ends of the furnace for the work and through which heated gases are discharged from the chamber about the work when the latter passes through the chamber, a number of direct fired burners for the furnace comprising a series of blocks of refractory material embodied in the refractory walled chamber and extending lengthwise thereof between the end walls, the blocks in said series collectively taking up a major portion of the lineal distance between said end walls, the radial distance from the inner faces of said blocks to the nearest line connecting corresponding points at the peripheries of the entrance and exit openings not exceeding the maximum dimension at the inner face of a block, the inner face of each block forming a part of the refractory lining for said chamber and serving as an independent source of heat, and means to supply combustible fuel individually to each burner.

14. Apparatus for progressively heating successive portions of work of elongated extent including a furnace comprising structure forming a refractory walled chamber having end walls each provided with an aperture therein. the apertures serving as entrance and exit openings at opposite ends of the furnace for the work and through which heated gases pass from the chamber about the work when the latter passes through the chamber, means for firing said chamber to an elevated temperature including several rows of burners comprising blocks of refractory material extending lengthwise of the chamber between the end walls, the blocks in each of said rows collectively taking up a major portion of the lineal distance between the end walls, said chamber in transverse section being of such shape and size that the burners are at close range to the work and distributed about the inner refractory lining of the chamber so that substantially uniform heating may be effected at all surface regions of successive portions of the work and permit slag to collect at the bottom of the chamber at regions removed from the burners arranged to effect heating of the underside of the work, the inner face of each burner forming a part of the inner refractory lining for the chamber and serving as an independent source of heat, and means for supplying combustible fuel individually to each burner.

15. Apparatus as set forth in claim 14 in which the structure is formed to provide an opening at the bottom of the chamber, and a removable closure for the last-mentioned opening to facilitate removal of slag collecting at the bottom ofthe chamber.

16. Apparatus for progressively heating successive portions of work of elongated extent including a furnace comprising structure forming a refractory walled chamber having end walls each provided with an aperture therein, the apertures serving as entrance and exit openings at opposite ends of the furnace through which heated gases are discharged from the chamber about the work when the latter passes through the chamber, said chamber in transverse section having two pairs of sloping walls diverging from the top and bottom thereof, a row of burners comprising blocks of refractory material at each of said sloping walls and extending lengthwise thereof between the entrance and exit openings, the blocks in each of said rows collectively taking up a major portion of the 21 lineal distance between the end walls, the inner face of each burner forming a part of the inner refractory lining for the chamber and serving as an independent source of radiant heat, and means to supp y aseous fuel individually to each burner for combustion at the inner face thereof to heat the latter to incandescence.

17. Apparatus for heating work of elongated extent including a horizontal furnace comprising structure forming a refractory walled chamber having end walls each provided with an aperture therein, the apertures serving as entrance and exit openings at opposite ends of the furnace for the work and through which heated gases pass from the chamber about the work when the latter passes in a single line transit and in endless procession through the chamber, means for rapidly heating successive portions of the work in the chamber by an intense heat release and high thermal head pro,- duced thereby 'which is of such magnitude that an abnormally high temperature will be produced in the chamber in the event of work stoppage therein, said last-mentioned means including a number of burners embodied in the refractory walled chamber between the end walls thereof and fuel supply means for individually delivering to said burners a combustible fuel mixture having as active components thereof a gaseous fuel and air, said fuel supply means including a pressure boosting device for delivering both of said active components under positive pressure to said burners, and means responsive to an abnormally high temperature in the chamber for shutting off the supply of the gaseous fuel component in the combustible fuel mixture and causing said device to deliver air only to said burners.

18. Apparatus for heating work of elongated extent including a furnace comprising structure forming a refractory walled chamber having end walls each provided with an aperture therein, the apertures serving as entrance and exit openings at opposite ends of the furnace for the work and through which heated gases pass from the chamber about the work when the latter passes in a single line transit and in endless procession through the chamber; means for firing said chamber to an elevated temperature including a number of burners in the refractory walled chamber between the end walls thereof. the inner face of each burner forming a part of the inner refractory lining for the chamber and serving as an independent source of heat; fuel supply means for delivering a combustible fuel and air to said burners, said fuel supply means including compressor means for delivering both the gaseous fuel and air under positive pressure to said burners, the number of burners in the chamber, the size and shape of the chamber in transverse section, and the pressure at which the mixture is supplied to the burners by the fuel supply means being correlated to effect rapid extent including a plurality of furnaces arranged closely together and in end to end relation. each furnace comprising structure forming a refractory walled chamber having end walls each provided with .an aperture therein; the apertures of the furnaces being substantially in alignment and serving as entrance and exit openings at opposite ends of each chamber from which heated gases are discharged from the chambers about the work when the latter passes through successive chambers; means for firing each of said chambers to an elevated temperature; roller means disposed between the furnaces and adlacent the entrance opening of the first furnace into which the work passes for guiding and frictionally moving the work through successive chambers; said roller means comprising sets of pinch rollers including top and bottom rollers; plvotally supported structures for carrying the top pinch rollers of the sets whereby the top pinch rollers are vertically movable with respect to the bottom pinch rollers and means for driving said pinch rollers including driving connections extending between the axes of the top pinch rollers and the regions at which the supporting structures therefor are pivotally mounted.

20. Apparatus for heating work pieces of elongated extent including a plurality of furnaces arranged closely together and in end to end relation, each furnace comprising structure forming a refractory walled chamber having end walls each provided with an aperture therein; the apertures of the furnaces being substantially in alignment and serving as entrance and exit openings at opposite ends of each chamber from which heated gases are discharged from the chambers heating of successive portions of the work by an intense heat release at a high thermal head; such heat release and thermal head developed thereby being of such magnitude that abnormally high temperatures will be produced in the chamber in the event of work stoppage: and means responsive to such abnormally high temperatures in the chamber for shutting off the supply of the combustible fuel mixture and causing said compressor means to deliver air only to the burners.

19. Apparatus for heating work of elongated about the work when the latter passes through successive chambers; means for firing each of said furnaces to an elevated temperature; roller means disposed between the furnaces and adjacent the entrance opening of the first furnace into which the work pieces pass and adjacent the exit opening of the last furnace from which the work pieces exit for guiding and frictionally moving the work through successive chambers; said roller means comprising sets of pinch rollers including top and bottom rollers; pivotally supported structures for carrying the to pinch rollers of each set whereby the top pinch rollers are vertically movable with respect to the bottom pinch rollers; the sets of pinch rollers being located and arranged adjacent the furnaces so that heated work pieces are always gripped and moved out of each chamber by the pinch rollers; said pinch rollers being hollow for circulating a coolant therethrough; and means for driving said pinch rollers including driving connections extending between the axes of the top pinch rollers and the regions at which the supporting structures therefor are pivotally mounted.

21. Apparatus for heating work of elongated extent including a furnace comprising structure forming a refractory walled chamber, a wall at each end of said furnace including a centrally disposed annulus of refractory material, said annuli forming entrance and exit openings for work at opposite ends of said chamber, said structure including a number of rows of burners comprising blocks of refractory material each having an opening therein, said blocks extending lengthwise of said chamber between the entrance and exit openings, the inner face of each burner forming part of the refractory lining for said chamber and serving as an independent source of radiant and convection heat, and means to supply gaseous fuel under pressure to each burner for combustion at the inner face thereof in said chamber to heat the latter to incandescence.

22. Apparatus for heating work of elongated extent including a horizontal type furnace comprising structure forming a refractory walled chamber including a floor and roof and opposed side walls forming a substantially cylindrical space, a wall of refractory material at each end of said chamber having an aperture therein, said apertures serving as entrance and exit openings at opposite ends of the furnace for work and through which heated gases are discharged from the chamber about the work when the latter passes through the chamber, said structure including rows of burners at the opposite side walls extending lengthwise of said chamber between the entrance and exit openings, each burner having an opening therein extending to said chamber, the inner face of each burner forming part of the refractory lining of said chamber and serving as an independent source of radiant and convection heat, and means to supply gaseous fuel to each burner for combustion in said chamber. 23. Apparatus for heating work of elongated extent including a furnace comprising structure forming a refractory walled chamber, a wall of refractory material at each end of said chamber having an aperture therein, said apertures serving as entrance and exit openings at opposite ends of the furnace for the work, and through which heated gases are discharged from the chamber about the work when the latter passes through the chamber, a hollow manifold at each end of the furnace adjacent to said end walls, each of said manifolds having inlet and outlet openings for circulating a coolant therethrough, said structure including a burner including a block of refractory material in said chamber between the entrance and exit openings, the inner face of said burner block forming a part of the refractory lining for said chamber and serving as a source of radiant and convection heat, and means to supply fuel to said burner block for combustion in said chamber to heat the latter.

24. Apparatus for heating work of elongated extent including a furnace comprising structure forming a substantially cylindrical refractory walled chamber, a wall of refractory material at each end of said chamber having an aperture therein smaller than said chamber, said apertures serving as entrance and exit openings at opposite ends of the furnace chamber for work to be heated when the latter passes through the chamber, said structure including a plurality of burners including blocks of refractory material extending in the walls to the chamber, each bumer block having an opening extending therethrough, the inner face of said blocks of refractory material forming part of the refractory lining of said chamber and serving as independent sources of radiant and convected heat, and means to supply fuel individually to each block for combustion in said chamber to heat the latter.

FREDERIC O. HESS.

REFERENCES crran The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,946,971 Harter Feb. 13, 1934 2,067,436 Coberly Jan. 12, 1937 2,113,426 Engels Apr. 5, 1938 2,150,534 Wiegand et al Mar. 14, 1939 2,215,080 Hess Sept. 17, 1940 2,398,398 Abbott Apr. 6, 1946 FOREIGN PATENTS Number Country Date 383,899 Great Britain June 18, 1931 

